Stacking system for paperboard blanks



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FIG. I0 I M/RCEA CAL IS 73647" June 23, 1970 M. CALISTRAT STACKINGSYSTEM FOR PAPERBOARD BLANKS ll Sheets-Sheet Original Filed Sept. 11,1967 m m? NM w w w md J am mt M w w 7 Q a m Lw mm fl June 23, 1970 M.CALISTRAT STACKING SYSTEM FOR PAPERBOARD BLANKS Original Filed Sept. 11,1967 ll Sheets-Sheet 11 3 w w A INVENTOR. M/RCEA CAL ISTP/JT 6 Ab/United States Patent US. Cl. 198-33 2 Claims ABSTRACT OF THE DISCLOSUREAn inverting conveyor for receiving consecutive individual stacks ofblanks from a storage conveyor in a manner to stand the stacks on theirleading edge; a first pivoting means for pivoting a first stack aboutits upstanding trailing edge to position the stack on a rising conveyorwith its top face up and a second pivoting means for pivoting a secondstack about its leading edge to position the stack on the risingconveyor with its top-face down; and, advancing means for thereafteradvancing the automatically inverted stacks to a downstream portion ofthe conveyor which then advances the stacks at a faster rate to drawthem away from the advancing means.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates generally to material or article handling and more particularlyto article piling or arranging apparatus. This is a division ofapplication Ser. No. 666,605, filed Sept. 11, 1967 now US. Pat. No.3,447,696.

Description of the prior art Corrugated paperboard blank-formingapparatus, commonly known as a corrugator, forms a continuous web ofcorrugated paperboard. Usually this web is longitudinally split into aplurality of parallel widths and each width is then cut laterally toform blanks of the material for making corrugated cartons such as boxes.The longitudinally advancing blanks are collected in stacks on adelivery conveyor which then discharges them transversely to the path ofblank travel for manual stacking into piles on a skid or other conveyor.

Despite constant efforts to improve the quality of box blanks thusproduced, the blanks still have a tendency to curl or warp, usually in adirection lateral to the web path. Warped blanks are difiicult toprocess by further processing machinery. To reduce the amount of warp inthe blanks, it is customary to stack them in large piles of smallerstacks of which smaller stacks are alternately placed face up and facedown. In this manner, the warped portions of one stack oppose the warpedportions of an alternate stack so that the weight of the pile tends toflatten the blanks.

Another inconvenience exists in that the advancing parallel adjacentblanks tend to become misaligned on the discharge conveyor so that theindividual blanks of adjacent stacks become interlaced. Thus, theattendants are required to manually separate these piles into discretestacks before alternate ones can be inverted.

Letchworth Pat. No. 3,297,174 discloses apparatus for invertingalternate small stacks of blanks. The Letchworth apparatus receives thestacks of blanks from the corrugator on a plurality of conveyor deliverybelts which are parallel but are at different levels so that one seriesof blanks can be placed on another to form a larger stack which isthereafter inverted.

The parallel delivery belts of Letchworth require individual heightadjustment for supporting the parallel advancing blanks whose width mayvary from order to order. A disadvantage of this arrangement is that theparallel streams of blanks exiting from the cut-off portion of thecorrugator are frequently interlaced. Therefore, it is ditficult for theblanks to drop to different levels as described by Letchworth. It isalso observed that it would be difficult to maintain the height of thefinal pile since it is formed by adding stacks to the top of the pile.Finally, turning alternate stacks of very large blanks degrees in onecontinuous motion requires considerable energy because of the large airresistance encountered by the blanks during such movement.

SUMMARY The present invention is particularly useful with and as a partof apparatus for automatically forming a pile of alternatley invertedstacks of blanks which pile may be of unlimited height. The apparatus isadaptable for use in conjunction with existing delivery conveyorswithout the need for complex adjustments. The apparatus includes atransverse storage conveyor adapted to receive stacks of blanks from acorrugator delivery conveyor; an inverting apparatus for receivingconsecutive individual stacks of blanks from the storage conveyor in amanner to stand the stacks on their leading edge, including anoff-setting device for off-setting alternate ones of the stacks relativeto the other ones of the stacks across their length, and a firstpivoting means for pivoting a first stack about its upstanding trailingedge to position the stack on a rising conveyor with its top face up anda second pivoting means for pivoting a second stack about its leadingedge to position the stack on the rising conveyor with its top facedown; and a stacking means for receiving alternately inverted stacksfrom the rising conveyor and forming them in a pile one under the otherby a lifting means for lifting each stack consecutively into engagementwith a pile support means, the lifting means operable to discharge apile of blanks of selected height onto subsequent processing apparatus.

The above and further objects and novel features of the invention willappear more fully from the following detailed description when the sameis read in connection with the accompanying drawings. It is to beexpressly understood, however, that the drawings are not intended as adefinition of the invention but are for the purpose of illustrationonly.

DESCRIPTION OF THE DRAWINGS In the drawings wherein like parts aremarked alike:

FIG. 1 is a diagrammatic front elevation of a conventional deliveryconveyor illustrating the usual discharge of interlaced blanks;

FIG 2 is a diagrammatic side elevation of an embodiment of the storageand loading conveyors and inverting mechanism illustrating stacks storedon the conveyor and a second stack being pivoted toward a top face-downposition on the rising conveyor;

FIG. 3 is a diagrammatic side elevation of an embodiment of the risingconveyor and stacking mechanism illustrating a pile of alternatelyinverted stacks of blanks being formed;

FIG. 4 is a plan view of FIG. 1',

FIG. 5 is a plan view of FIG. 2;

FIG. 6 is a plan view of FIG. 3;

FIG. 7 is a partial view of the inverting mechanism of FIG. 2illustrating a first stack being pivoted toward a top face-up positionon the rising conveyor;

FIG. 8 is a section view taken along the line VIII VIII of FIG. 2illustrating an ofi-set mechanism for laterally off-setting alternatestacks of blanks;

FIG. 9a is an elevational view of a portion of the rising conveyorillustrating the types of pivoting fingers and advancing fingers used topivot a first stack of blanks and advance both first and second stacksof blanks;

FIG. 9b is a plan view in partial cross-section of one of the pivotingfingers of FIG. 9a illustrating its connection to the chains used on therising conveyor;

FIG. 10 is a partial view of the stacking mechanism of FIG. 3illustrating a squaring mechanism for aligning the stacks prior tolifting them to form the pile;

FIG. 11 is a schematic illustration of the sequence of pivoting thestacks in the inverting mechanism into alternate face-up and face-downpositions; and

FIG. 12 is a schematic diagram of the controls used for controlling thefunctions of the invention.

THE PREFERRED EMBODIMENT In the manufacture of corrugated blanks, a webof corrugated paperboard is formed and then slit into a number ofparallel streams of desired width. These streams are subsequently cuttransversely to form parallel streams of blanks. The cutting operation,by its nature, inherently has a tendency to skew the blanks so that theyare not exactly parallel to the flow of blanks. Accordingly, overlappingof the blanks between the parallel stream occurs. This overlapping iscommonly known as interlacing. Stacks of interlaced blanks areillustrated in FIGS. 1 and 4.

Referring now to FIGS. 1 and 4, piles of interlaced blanks A and B andshingled blanks C and D (a portion of one blank resting upon the nextadjacent lower blank) are shown preparatory to lateral discharge from aconventional delivery conveyor, generally designated 10, of a corrugator(not shown). Delivery 10 may be of the type shown in Lopez Pat. No.3,079,150 which includes belts 12 for advancing the blanks downstream inshingled fashion where they are temporarily halted by a gate '14. Beyondgate 14, delivery 10 includes a plurality of longitudinally mountedrollers at a lower elevation than belts 12. When gate 14 is removed fromthe leading edges of the shingled blanks C and D, they are advanced bybelts 12 causing them to fall one on top of the other upon rollers 16 toform piles A and B. A back-stop 18 is provided to halt the forwardprogress of the blanks and is adjustable upstream and down toaccommodate the length of blanks being handled. Hereinafter, the lengthof the blanks on stacks refers to their longitudinal dimension along thedelivery 10 as viewed in FIG. 4.

When piles A and B reach a selected height, gate 14 is moved tointercept the flow of blanks C and D. Thereafter, rollers 16 are drivento discharge the piles A and B upon a storage conveyor assemblygenerally designated 20. When pile B is completely clear of delivery 10,the foregoing process is repeated.

Although only two parallel streams of blanks are shown, it is notuncommon to have the initially formed we'b slit into four and sometimesas many as seven streams. The slit web is usually divided into an equalnumber of narrower webs of which one-half are guided into an uppercut-off knife and the other half into a lower cut-off knife. Theshingled blanks C and D are discharged from one of the knives. Anotherdelivery 10 is provided to handle the discharge from the other knife.Either or both deliveries 10 may be provided with the present inventionwhich is illustrated herein to handle four streams from each delivery atmaximum corrugator speed and more at lesser corrugated speeds.

INVERTER AND OFF-SETTING ASSEMBLIES Inverter assembly 22 receivesindividual stacks of blanks and inverts alternate ones of the stacks toa facedown position upon a rising conveyor assembly 90. The remainingstacks are placed on conveyor in a face-up position.

Inverter 22 also offsets alternate stacks in a lateral direction asillustrated in FIG. 8. This off-set condition 4 contributes to ease ofhandling of the stacks in subsequent processing operations, providing agripping surface which the attendants may use in moving the stacks.

As best illustrated in FIG. 2, a stack B is inverted to a face-downposition by pivoting the stack B about its leading edge, as shown by thedotted lines. Pivoting is accomplished by an inverting lever 92 adjacentthe bottom face of stack B. After stack B has been laterally offset,lever 92 is actuated to pivot the stack about its leading edge so thatit falls face down upon conveyor 90. Thereafter, stack B is advancedalong the conveyor by an advancing finger 94 and stack A (now on theconveyor 26) is discharged into inverter 22 by loading conveyor 26.

Stack A, FIG. 7, is pivoted about its trailing edge by a roller finger96, as shown by the dotted lines so that it falls face-up on risingconveyor 90. Thereafter, stack A is advanced by a subsequent advancingfinger 98.

FIG. 11 illustrates, in panels (D through the inverting sequence of fourstacks A, B, C and D. The stacks are lettered and the heavy lineadjacent the face of the stacks indicates the relative face positions ofthe stacks during operation of inverter 22 and rising conveyor 90.Certain of the roller and advancing fingers are disengaged whenextra-width stacks are being handled. This feature will be subsequentlydescribed. Coincidentally, reading panels 6), and vertically shows thestacks A, B, C and D to be alternately inverted to face-up and face-downpositions.

Inverter assembly 22, FIGS. 2 and 8, comprises side guides in the formof upright angles and 102 for receiving the stacks as they fall fromloading conveyor 26. Each of the guides has a side leg 104 for engagingthe ends of the stacks and a bottom leg 106 engaging the underside ofthe stacks to support them in an upright position. Slide block 108secured to leg 106 of guide 100* and mounting block 110 secured to leg106 of guide 102 support the guides on a pair of support rods 112.

INVERTER ASSEMBLY After each stack A or B has been offset, stack A isinverted to a face-up position and stack B is inverted to a face-downposition. As previously mentioned, stack A is pivoted about its trailingedge by a roller finger 96 and then advanced along rising conveyor 90 byadvancing finger 98. Stack B is pivoted about its leading edge byinverting lever 92 and then advanced along rising conveyor 90 byadvancing finger 94.

The inverting lever 92 is pivotably supported between a clevis bracket124 by a pin 126 passing through lever 92 and bracket 124. Bracket 124is secured to rising conveyor 90. Lever 92 includes an upstanding legportion 128 which, in its retracted position, is on the same plane withthe leg portions 102 of guides 100 and 102. That is, leg 128 liesimmediately behind the bottom face of a stack A or B in the inverter 22.Lever 92 includes a short leg 130 formed at a right angle with leg 128and connected to a pneumatic ram 132 by a conventional pin connec tion134. Ram 132 is pivotably secured to rising conveyor 90 by a similar pinconnection 136. After a stack B in the inverter 22 has been offset, aspreviously described, ram 132 is actuated thereby pivoting lever 92about pin 126 as shown by the dotted lines in FIG. 2. Upstanding leg 128pushes against stack B thereby pivoting it about its leading edge sothat it falls face down on conveyor 90. Thereafter, advancing finger 94is moved forward to engage the trailing edge (previously the leadingedge) of stack B and advance it along conveyor 90. Simultaneously, ram132 is retracted to return lever 92 to its original posi tion.

To invert a stack A in inverter 22 to a face-up position on conveyor 90,a roller finger 96 is advanced against the lower portion of the back ofstack A after the stack has been offset. A small roller 136 carried byfinger 96 pushes against the stack thereby moving its leading edgeforward and letting its trailing edge slide down the leg portions 106 ofguides 100 and 102. The end result is that stack A is generally pivotedabout its trailing edge until it rests on conveyor 90. As the stackslides down onto conveyor 90, finger 96 continues to advance along theconveyor, with the small roller 136 rolling along the bottom of thestack, until finger 96 is forward of stack A. Thereafter, advancingfinger 94 is moved forward to engage the trailing edge of the stack andadvance it along conveyor 90.

RISING CONVEYOR Rising an advancing conveyor 90 advances the ofiF-setand inverted stacks to an entry conveyor 138 from which the stacks aredischarged into a stacker portion 140. Conveyor 90 comprises a pluralityof stack supports 142a, b, c, d and 2 extending substantially between alower sprocket shaft 144 and an upper sprocket shaft 146. As bestillustrated in FIGS. 2 and 3, supports 142 are mounted upon a pair ofcross-members 148 which have their ends supported by longitudinallyextending frame members 150a, 15% secured to upstanding frame portions70a, 70b and 1520, 15217.

Sprocket shaft 144 is rotatably mounted between frame portions 70a, 70band has an extended portion 154 extending beyond frame portion 70b uponwhich is mount-- ed a pulley wheel 156. A speed reducer 158 is mountedon frame portion 70b and carries a clutch 160 thereon, the clutch beingsubstantially identical to clutch 72 previously described. Clutch 160 isdriven by the rotation of speed reducer 158 which is in turn rotated bya pulley wheel 162 mounted thereon connected by a V-belt 164 to a pulleywheel 166 mounted on output shaft 78 of motor 76. An output pulley wheel168 on clutch 160 drives pulley wheel 156 through a V-belt 170 andthereby rotates sprocket shaft 144.

Upper sprocket shaft 146 is rotatably mounted between frame portions172a, 172b of entry conveyor 138. Pairs of roller chains 174 located inspaces provided between stack supports 142 encircle sprockets 176 and178 mounted respectively on the lower sprocket shaft 144 and uppersprocket shaft 146. The path traveled by the upper runs of chains 174carries them over sprockets 180 secured to pulley shaft 182 of entryconveyor 138 for driving shaft 182.

As best illustrated in FIGS. 9a and 912, each pair of chains 174 carriesroller fingers 96 and advancing fingers 94 therebetween so that thefingers travel with the chains. Four kinds of fingers, 94, 96, 184, and186 are used. Each of the fingers includes a U-shaped body portion 183as viewed in FIG. 9b, having a lug portion 188 on each leg thereofextending beside the adjacent chain 174. Chain 174 includes a link 190extending upward so as to overlap lug portions 188. Pins 192 extendthrough holes provided in both the lugs 188 and links 190 to pivotablysupport the fingers to the chains. Pins 192 are retained by cotter pins194.

Fingers 94 and 184 also include lug portions 196 similar to and spacedfrom lugs 188 to overlap a subsequent link 190 in chain 174. Pins 192likewise connect lugs 196 to links 190 so that fingers 94 and 184 willnot pivot about pins 192 in lugs 188.

Fingers 96 and 186 include lug portions 198 extending beneath chains 174between which a roller 200 is carried by a pin 202 passing through theroller 200 and lugs 198. Pin 202 is retained by cotter pins 194. Thus,it can be seen that fingers 96 and 186 are free to pivot about pins 192in lugs 188 as indicated in the right-hand portion of FIG. 9a. Acounterweight 204 is secured between the legs of the U-shaped bodyportion of fingers 96 and 186 by a bolt 206 and a nut 208 clamping thelegs against the counterweight. The counterweight causes the stackengaging faces 210 of the fingers to lie substantially flat with respectto the chains 174 as viewed to the extreme right of FIG. 9a.

Referring now to FIGS. 2 and 3, conveyor 90 also in cludes a rollersupport 212 beneath the upper run of each 6 pair of chains 174 forengaging rollers 200 of fingers 96 and 186 to maintain the fingers in anupright position as viewed in FIG. 9a. However, roller supports 212 maybe lowered to the position shown by dotted lines in FIGS. 2, 3, 9a, and11. When in the lowered position, fingers 96 and 186 will lie fiat aspreviously explained.

lowering of roller supports 212 is accomplished by pivotably supportingthem on frame members 150a, 150-b. Pivot rods 214 are provided betweenframe members 150a, 150b. Pivot rods 214 are provided between framemembers 150a, 1501? with pivot arms 216 secured thereto in a positionbeneath roller supports 212. Pivot arms 216 are connected to thesupports 212 by a conventional pin connection 218 which allows thesupports to swivel with respect to the pivot arms. Thus, when the pivotarms 216 are rotated clockwise, as viewed in FIGS. 2 and 3, the rollersupports 212 will be lowered to the position indicated by the dottedlines. An operating lever 220' is provided on one end of one of pivotrods 214 for rotating the rod. A suitable clamp (not shown) is providedto lock the pivot rod in the desired position when the supports 212 arein either the raised or lowered position.

Thus, it can be seen that when the supports 212 are in the lowerposition, fingers 96 and 186 will traverse the upper run of chains 174in a flat position, as viewed in FIG. 9a, since rollers 200 do notcontact the supports 212. However, when supports 212 are in the raisedposition, rollers 200 will flip the fingers 96' and 186 into an uprightposition as they approach the supports 212. A lead-in portion 222 onsupports 212 aids in pivoting the fingers to an upright position.Fingers 96 and 186 merely hang free from pins 192 during the traverse ofchains 174 along the lower run between the sprockets 176 and 178.

The length of rising conveyor is made to accommodate the widest stack tobe handled. As viewed in FIGS. 2 and 3, which may conveniently be joinedto give a complete picture of conveyor 90, stack A is being dischargedonto entry conveyor 138 as stack B is being inverted to fall face downon conveyor 90. Thus, sufficient space must be allowed between finger 98and the finger 94 approaching inverter 22. For example, if the maximumwidth stack to be handled is five feet, a space of about six feet isrequired between the fingers. However, if the stack width is less thanhalf the maximum width, that is, two and onehalf feet or less, obviouslytwo stacks can be accommodated between fingers 98 and 94. This explainsthe reason for providing some of the fingers with rollers 200 supportedby roller supports 212.

FIG. 11 illustrates stacks of two and one-half feet or less beingprocessed. For stacks A and C two fingers are required; roller finger 96to invert the stack to a face-up position and advancing finger 94 toadvance the stack along the conveyor. On the other hand, stacks B and Drequire only an advancing finger 186 to advance it along the conveyor.Thus, three fingers are required for each set of stacks A-B and 0-D.Since a set of narrow stacks can be accommodated simultaneously onconveyor 90, obviously another set of three fingers can be carried onthe lower run of chains 174. Accordingly, a total of six fingers areprovided at the proper sequential spacing on chains 174. However,appropriate ones of the fingers may be lowered to an inoperativeposition by lowering roller supports 212 so that only three fingersremain upright for handling stacks wider than two and one-half feet.

Obviously, lowering three adjacent fingers will leave three fingersupright at a short spacing. Therefore, selected ones of the fingers arelowered to leave three fingers upright at the required spacing for widestacks. FIG. 11 illustrates in dotted lines those fingers to be loweredwhen wide stacks are handled.

As previously mentioned, finger 96 is provided with a roller 136 topermit the finger to pass beneath stack A after the stack has :beeninverted thereby. Finger 184 is likewise provided with a roller 136.Roller 136 is carried between upstanding lug portions 224 of fingers 96and 184 7 by a pin 226 passing through both the roller 136 and lugs 224.Cotter pins 194 retain pin 226, as illustrated in FIG. 9b.

Although the foregoing arrangement of conveyor 90 has been described forwide stacks of from two and one-half to five feet and narrow stacks oftwo and one-half feet and less, obviously, the proportions may bedesigned to handle other size stacks which may be manufactured.

Conveyor 90 normally runs continuously. However, in the event that astack is not present in loading conveyor 26, a signal is provided todisengage clutch 160 so that conveyor 90 is not driven. The signal alsoenergizes a brake 228 (similar to *brake 86) carried by an extension230' on sprocket shaft 144 extending beyond frame portion 70a. Thesignal will be discussed further in the control portion of thespecification. Brake 228 is used to stop the chains 174 immediatelyafter the signal is received so that the fingers will remain in timedrelation to loading conveyor 26. Otherwise, a stack could be loaded ininverter 22 with the fingers in the wrong position to maintain theinverting sequence.

ENTRY CONVEYOR Entry conveyor 138 removes stacks of blanks from conveyor90 at a slightly faster speed than they are traveling so that they moveaway from the advancing finger to allow the finger to clear the stack asit passes over sprocket 180 and thereafter around sprocket 178. Thestacks are also made level for entry into stacker 140.

Conveyor 138 comprises a pulley shaft 182 mounted for rotation betweenframe portions 152a, 152b and a pulley shaft 232 mounted for rotationbetween frame portions 234a and 234b, the latter frame portions beingcommon to stacker 140. Pulley wheels 236 are mounted on shaft 182adjacent each of the sprockets 180 as shown in FIG. 6. Correspondingpulley wheels 238 are mounted on shaft 232. Endless belts 240 encirclecorresponding pairs of pulley wheels 236 and 238. Pulley wheels 236 aredriven by the rotation of shaft 182 which is in turn driven by sprockets180 being rotated by chains 174. Sprockets 180 are somewhat smaller thanthe pulleys 236 so that the surface speed of belts 240 is greater thanthe velocity of the advancing fingers. An increase in speed of about 5%is usually sufficient to allow the fingers to clear the stacks beingadvanced by the entry conveyor 138.

Stack A is received by inverter 22 and guided into an upright position.The guides 100 and 102 are operated to laterally offset the stack. StackA is pivoted about its trailing edge by a pivoting finger carried on therising conveyor 90 so that it falls face up on the conveyor. Thereafter,an advancing finger carried by the conveyor engages the trailing edgeand advances stack A along the conveyor. Meanwhile stack B on thestorage conveyor 24 has been advanced upon conveyor 26 to the positionpreviously occupied by stack A. At the proper interval of rotation ofchains 174 on conveyor 90, conveyor 26 will be rotated to load stack Binto inverter 22. Stack B is offset and then pivoted about its leadingedge by the inverting lever 92, so that it falls face down upon conveyor90. Thereafter an advancing finger on chains 174 engages its trailingedge and advances it along conveyor 90. Meanwhile stack A, which haspreceded stack B, is received upon entry conveyor 138 which rotatesfaster than chains 174 so that the trailing edge of stack A ad vancesfaster than the advancing finger so that the finger will clear the stackas it begins its return along the lower 8 run of chains 174. Entryconveyor 138 loads stack A into stacker 140.

I claim:

1. An advancing conveyor having an upstream portion and a downstreamportion for alternately inverting and advancing stacks of blanks, placedsequentially on said upstream portion in a substantially uprightposition, toward said downstream portion from said upstream portion,comprising:

support means for supporting said stacks on said conveyor; firstinverting means operatively associated with said conveyor for invertinga first one of said stacks to a face-up position on said support;

second inverting means operatively associated with said conveyor forinverting a second one of said stacks to a facedown position on saidsupport;

first advancing means operatively associated with said conveyor foradvancing said first stack along said conveyor from said upstreamportion toward said downstream portion; and second advancing meansoperatively associated with said conveyor for advancing said secondstack along said conveyor sequentially behind said first stack;

said first and second advancing means having upstanding portions forengaging the trailing edges of said stacks for advancing the same alongsaid upstream portion of said conveyor and onto said downstream portionat a first rate of speed,

said downstream portion operative to advance said stacks at a secondrate of speed faster than said first rate of speed,

whereby said stacks are drawn sequentially away from said first andsecond advancing means so that said first and second advancing means canbe returned to a position for engaging subsequent sequential first andsecond stacks of blanks placed on said upstream portion.

2. The advancing conveyor of claim 1 wherein said first and secondadvancing means comprise first and second fingers secured between a pairof laterally spaced endless chains at selected positions therealong,

said chains encircling both a first sprocket wheel adjacent the upstreamend of said upstream portion of said conveyor and a second sprocketwheel adjacent the downstream end of said upstream portion of saidconveyor,

said second sprocket wheel positioned beyond the upstream end of saiddownstream portion of said conveyor,

whereby said advancing fingers advance said stacks onto said downstreamportion at said first rate of speed.

References Cited UNITED STATES PATENTS 814,442 3/1906 Graham 198-76 X2,780,342 2/1957 Good 198--34 X FOREIGN PATENTS 392,367 9/1965Switzerland.

EDWARD A. SROKA, Primary Examiner U.S. Cl. X.R. 19876

